1. Field of the Invention
The present invention relates to backlight modules. A backlight module is proposed with a reduced number of lighting bars and LEDs. This solves the problem of non-uniform brightness seen in conventional backlight modules thanks to a uniform backlight source.
2. Description of Related Technology
A liquid-crystal display device is a passive display device without auto-lighting function and which has to install a light source to provide the required display light source for the display panels. Therefore, the display quality of liquid crystal display devices are is dependent upon the backlight modules providing a light source with sufficient brightness to give the display panel a uniform brightness.
Generally, a backlight module can be divided to front light type and back light type, and in fact can be further divided into sidelight type structure, hollow type structure and direct type structure. Therefore, a small-sized backlight module with sidelight type structure can saved manpower and materials, but a large-sized backlight module with sidelight type structure has the drawback of providing non-uniform lighting and being difficult to manufacture. A backlight module with the direct type structure, where there is no need to set the light guide plate, was created as a result. The direct type structure is used in the large-sized backlight module, and the backlight module with the direct type structure can take light from the source, reflect it with the reflecting plate, and scatter it uniformly with the diffusion plate where it can come out the front side. Therefore, the light source can be installed with two or more light tubes according to the size of the panel and thus the uniformity of the light irradiation can be increased. However, the slender light tubes are costly to produce and easy to break. And the installation of reflective plates is another technical question that still awaits a satisfying answer.
As such, a technology recently appeared on market that uses light-emitting diodes used on a backlight module. Due to the light-emitting diodes' small size, low power consumption, long life, short reaction time and strong shock-resistance, they are widely used as a lighting or backlighting light source, as a replacement for traditional light sources like incandescent light bulbs, cold cathode tubes or fluorescent tubes.
Generally, when the light-emitting diodes are installed on a backlight module, they are connected by conductive circuits in series connection or parallel connection and mounted on circuit board which is referred to as a “light bar”.
In order to make the light source irradiate uniformly to the plate and improve problems like insufficient light or irradiation non-uniform, the conventional LCD display devices usually have several light bars mounted on the back plate and/or several light emitting diodes mounted in each light bar, which in turn increases the overall cost of the LCD display. Additionally, as shown in FIG. 1, due to the fact that LEDs are a directional light source, the direction and angle of the light source are limited. Thus, it is likely that the dark area 90 of the display panel will appear, due to bad locations or insufficient number of LEDs of the backlight modules. In order to solve these problems, however, merely adding LEDs on the light bars or adjusting the locations of the light bars on the back plate would have the result that the LEDs could not be used to their full potential and their lighting efficiency would suffer. Furthermore, the weight, volume and cost of the overall backlight module and liquid crystal display device would increase.
Therefore, as far as market demand is concerned, there is an urgent need for the design of a backlight module that provides a uniform backlight light source while reducing the amount of LEDs used so as to lower overhead costs.